Extender for binoviewing

I think I need to get an extender to get my binoviewer to come to focus. Does anyone know
a good extender that I can put into the drawtube of the telescope and insert my diagonal/binoviewer
into it to get some more out focus travel? I am using a Denk binoviewer/multipurpose OCS in a SV105 refractor.

I am not sure how long I need and a variable extender would be ideal. I know I need at least 2 inches and perhaps as much as 4 inches of additional out travel. Maybe a variable wouldn't have the stability needed to hold the weight of the binoviewer though. Also, dual lock down screws would also be great to keep the binoviewer/diagonal from rotating although the only one I saw (Televue) had one screw. Thanks.

Dave Adams

Hi Dave
Try removing the OCS cell. As I remember that was part of the reason for the OCS cell was to lengthen the light cone so most normal scopes would come to focus. Most of the "BV Ready" scopes were shortened so the BV didn't need the OCS cell, and usually included the extention tube for normal use. You may not need the OCS cell. Someone correct me if I am wrong.
Buck